An optical pickup of an optical disk apparatus has the following problem: a large astigmatism of an objective lens outgoing side spot will degrade record/playback characteristics on an optical disk.
As one of correcting such an astigmatism, there is proposed a method of adjusting collimation with an anamorphic prism provided between a collimate lens and an objective lens (for example, refer to Patent Document 1, from the 1st line in the left upper column to the 2nd line in the right upper column at Page 2).
Patent Document 1 Japanese Patent Laid-Open No. 64-76011
However, the above-mentioned method of correcting astigmatism with the anamorphic prism has the following problem: the anamorphic prism causes the optical pickup to be complicated and enlarged.
Furthermore, fine adjustment of an angle of an erecting mirror for erecting optical beams perpendicularly to the optical disk can correct the astigmatism, however, this requires an adjusting mechanism for varying the angle of the erecting mirror. Accordingly, there is a problem of the fine adjustment method not being applied to a thin type optical pickup.